Cigarette is a small paper cylinder filled with dried and finely cut tobacco leaves therein for smoking. At present, the natural tobacco raw material directly used in cigarette industry includes raw stuff produced by tobacco leaves and stalk, for which corresponding large manufacturing equipments are provided.
It is known that natural tobacco raw material contains nicotine and nitrosamine and will generate tar and carbon monoxide during its burning, which are harmful to human's health. The smoking flavor is significantly affected by various factors such as variety, planting area, cultivating method, remained leaves number, maturity and aging, etc. The heavy wooden smell and the bitter, hot, and harsh taste brought about by the cut stem filled in the cigarette also restrict the development of the tobacco industry. It is a very important and long term researching subject for cigarette industry to decrease the harmful components, to improve smoke flavor of the tobacco raw material and consequently to improve the quality of the tobacco raw material. Recent years, many studies on improvement of tobacco raw material focused on the following aspects.
1. Additional Measures Taken in the Cigarette Production.
Aging, moisture regaining, conditioning, cut tobacco drying, expanding of tobacco raw material, etc, which are generally adopted, improve the quality of tobacco raw material only in certain extent but cannot play a key role on the improvement of tobacco raw material.
2. Addition of Reproduced Tobacco Slice.
Chinese patent No. 93120477.1 disclosed a process and apparatus for manufacturing tobacco slice by papermaking process. By using some leftovers such as waste tobacco leaves, tobacco fines, powder, and stalks as raw material, the process is implemented by the steps of grinding, impurity removal, drying, and extracting effective components by solvent to obtain extract liquor and extraction residues, the extract liquor being concentrated, separated from harmful components, and concentrated into extract to get the coating liquid, and the extraction residues being pulped, added with outer fiber, papermade into base paper, then coating the coating liquid on the base paper, drying and finally obtaining reproduced tobacco slice. The natural tobacco raw material directly used in cigarette industry generally maintains the original material without grinding and reproduction. The reproduced tobacco slice as a raw material is added into the natural tobacco raw material directly used in cigarette industry with a proportion being generally controlled under 10%, internationally 35% in maximum, in consideration of traditional smoking flavor and quality. Thus, the reproduced tobacco slice can improve tobacco components only in certain extent but not play a key role on the improvement of tobacco raw material. The reproduction of tobacco slice has the advantage of utilization of waste and the disadvantages of complexity, high cost and high addition of non-tobacco substances.
3. Addition of Functional Additives.
A lot of measures have been adopted to reduce harmfulness of cigarette, such as adding potassium salt for decreasing pyrolysis temperature so as to reduce the CO amount in smoke, and adding specific microorganisms for the degradation of nicotine, nitrite, and tobacco-specific nitrosmaines (TSNAs), etc. However, such additions will be liable to cause unknown safety problems of harmfulness and toxic, and may change the traditional smoking flavor of the cigarette. Improving smoking flavor merely by addition of aroma components is unsatisfactory since the bad flavor is not removed.
4. Washing Tobacco (the Cut Stem Made of Stalk).
Chinese patent application No. 201010563347.9 discloses a method for reproducing cut stems, which comprises: washing cut stem with prepared basic or acid washing solvent to remove off-flavors components, wherein the washing solvent is discarded or used for other purpose, and subsequently dehydrating to a moisture of 50˜90%, immersing the dehydrated cut stem in the feed liquid prepared by 1˜10 parts of sugar, 0.01˜3 parts of nicotine, 0.1˜1 part of potassium, 1˜40 parts of aroma components in tobacco, 0.1˜5 parts of antistaling agents, 0.1˜1 parts of pigment, and 35.71˜97.6 parts of water or organic solvent by weight, then dehydrating to a moisture of 50˜90%, and finally drying to a dryness that meets the requirement of stem expanding process. The defects of the above technical solution are: 1) the washing solvent with complex composition causes unknown problems affecting smoking safety; 2) there were great differences between the composition of the feed liquid and that of natural tobacco, therefore the smoking flavor of the reproduced cut stem is greatly different from that of natural tobacco; and 3) the lack of recycle measure of washing liquid causes environment pollution.
5. Extraction of Tobacco (Cut Stem of Stalk).
Chinese patent application No. 201110265037.3 filed by the present applicant discloses a method of manufacturing tobacco cut stem. In this method, the cut stalk is extracted with solvent through a series of extraction devices at a ratio of mass of material to solvent being 1:20, 20˜60 mm, solvent temperature of 20˜50° C., and extraction mode being downstream. The extract liquor is discarded. After a solid-liquid separation by means of squeezing and centrifugation, the cut stem is backfilled by spraying the feed liquid having a concentration of 30˜40% at 0˜40° C. and with a proportion of addition at 40˜20%. The backfilled cut stem is pretreated to lower down its moisture from about 65% to about 35%, and then is tower puffed or airflow dried so that the taste of cut stem can be improved and the harmful components such as tar and carbon monoxide in cut stem are reduced, which increases the filling value and the utilization of cut stem. The disadvantages of the above technical solutions are: 1) the blending of the backfilling feed liquid is too complicated and expensive, which goes against practical application and production; 2) lack of the recycle measures of the feed liquid will cause environmental problems; and 3) too much addition of non-tobacco substance could easily lead to unknown problems in smoking security.
In conclusion, in the researches and practices for improving tobacco raw material, the waste tobacco leaves in cigarette production as a raw material are grinded and reproduced to obtain tobacco slice which cannot play a key role in the improvement of tobacco raw material due to the limitation of the proportion of addition, and has the disadvantages of complicated process and high cost. The non-tobacco substances of the specific additives in original tobacco raw material will lead to new and unknown safety problems and affect the traditional smoking flavor. Moreover, addition of aroma components solely cannot achieve a satisfactory effect as the bad flavor hasn't been removed. The method, which comprises washing or extracting the original cut stem, removing the undesired extract liquor, and backfilling into the cut stem with prepared feed liquid, is liable to generate new or unknown safety problems as the process is still unmatured. Further, the method still has the disadvantages that the smoking flavor is greatly different from that of natural tobacco, the preparation is too complicated for practical operation, and lack of trecycle measures for the washing liquid and the extract liquor will cause environment pollution.
It is undoubtedly a determinant technical measure to directly improve the tobacco raw material directly used in cigarette industry on the basis of keeping original form of material. However, at present, relevant researches and corresponding practices in this respect are not matured and satisfying. There are still some problems to be solved. The corresponding equipments are also not matured and some aspects are still nearly in blankness.